How popular is Darrah?

Darrah is a rare given name for females but a very popular last name for all people (#9064 out of 150436, Top 6%). (2000 U.S. Demographics)

Which version is better?

with its source form and related girl names. Popular variation forms of Darrah (not ranked) are Dara, Daria(#1681 in 2015), Darian and Darice. Other variants, like Darah, are seldom used. Usage of these forms of Darrah was at its peak 21 years ago (median #1208) and is now much diminished. (Top Baby Names, 2015)